Mealybug biocontrol in New Zealand vineyards: A study of the biology and behaviour of the mealybug parasitoid Anagyrus fusciventris

Abstract

An essential part of biological control programs is to perform a comprehensive assessment of the prospective biological control agent to adequately achieve control of a pest. Parasitoids are a popular choice for biological control due to their relative high levels of specificity which reduces the risk of host switching and non-target impacts. Pseudococcus calceolariae and Pseudococcus longispinus are two polyphagous mealybug species that are major pests in the New Zealand wine industry. The greatest risk presented by these two mealybug species is their ability to vector the Grapevine leaf roll virus (GLRaV-3). One of mealybug natural enemy present in New Zealand is the solitary endoparasitoid Anagyrus fusciventris. A. fusciventris is being considered as a potential augmentative biological control agent for these two mealybug species. However, there is little published information on this species. In this thesis, I have conducted various experiments to help begin filling the knowledge gaps surrounding A. fusciventris. Firstly, development at six different temperatures were tested for both mealybug hosts. Temperature had the greatest impact on development but a sex and host effect was also observed. Secondly, CLIMEX software was used to model the potential geographic distribution using the data obtained from the development experiment and known A. fusciventris occurrences. In New Zealand, distribution is largely confined to the North Island with patches of marginally suitable habitat located at the north of the South Island. Thirdly, host volatiles were tested using a Y-tube olfactometer. A. fusciventris showed an attraction to P. calceolariae pheromones but an aversive response to P. longispinus cues. Fourth, sequential no-choice oviposition tests were used to assess the ability of A. fusciventris to parasitise the target mealybug species. It was found that, on average, A. fusciventris oviposited most of their eggs in the first host species they encountered. Finally, field sampling in two different management style blocks at an Auckland vineyard were used to monitor the seasonal phenology of A. fusciventris. Abundance peaked in February and declined completely during the winter months when hosts were scarce and temperature too cold. The implications of this research on the future of A. fusciventris as a biological control agent is that there is potential for successful pest control. A. fusciventris has shown an almost equal ability to parasitise both mealybug species. However, there are environmental constraints on where A. fusciventris could be used for biological control. Additionally, any mass releases of this species would need to be timed to coincide with suitable environmental conditions and host availability.